DESCRIPTION: A central feature of theories regarding cerebellar function is their emphasis on the role of this structure in motor learning. Damage to this subcortical structure produces impairments not only in the control of movement, but also in the acquisition and consolidation of new motor skills. A description of cerebellar function that emphasizes motor learning, however, is insufficiently constrained given the broad range of skills encompassed by this term. The proposed studies are designed to clarify the boundary conditions of the cerebellum in motor learning, seeking to identify those features that are dependent on the integrity of the cerebellum as well as those features that do not involve the cerebellum. A set of the experimental tasks will be employed in which the core component of skill acquisition requires learning novel spatial relationships or novel spatiotemporal patterns. These tasks will be used to test two primary hypotheses. First, cerebellar involvement in motor learning will be more pronounced for tasks that emphasize plasticity in the temporal domain compared to tasks that emphasize plasticity in the spatial domain. Thus, the cerebellum will be essential for the acquisition of skills that exploit temporal regularities in the environment or require the modification of the temporal relationship between a movement and the resulting sensory consequences. In contrast, this hypothesis predicts that the cerebellum will not be directly involved in the development of skills that depend on the establishment of novel spatial representations or transformations. Second, a cerebellar-prefrontal network is hypothesized to support the maintenance of stimulus-response associations, an action-oriented form of working memory. These representations are a prerequisite for many forms of motor learning. Tasks that tax this network will involve the cerebellum, even if the primary locus of learning is extracerebellar. The performance of patients with cerebellar disorders will be compared to that of matched control participants. This methodology will be complemented by neuroimaging studies involving neurologically healthy individuals. PUBLIC HEALTH RELEVANCE Identification of the functional domain of the cerebellum in motor learning is important for the development of models of cerebellar function and for understanding the patterns of connectivity between the cerebellum and the cerebral cortex. The results should be of clinical relevance, allowing therapists to design rehabilitation programs that are tailored to either target or minimize impaired functional capabilities.